(1) Field of the Invention
The present invention relates to the transport of pulverized material and particularly to the fluidization of a stored quantity of such material and the subsequent distribution of the thus fluidized material. More specifically, this invention is directed to apparatus for the handling of pulverized material and particularly to a system which permits the reliable and economic delivery of such material into a stream of carrier gas for transport a consuming device. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus for such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the delivery of pulverized coal or lignite to the tuyeres of a blast furnace. The advantages incident to the injection of a pulverized solid fuel into a blast furnace are known in the art and a system for transporting pulverized solid fuel for this purpose is disclosed in copending U.S. patent application Ser. No. 158,612 filed June 11, 1980 and assigned to the assignee of the present invention. In the installation of the referenced copending application, the pulverized fuel is extracted from the bottom of a final storage container, via extraction orifices which are provided with rotary feeders, and pneumatically conveyed to each of the tuyeres of a blast furnace. The system of the copending application also includes an intermediate material storage tank or chamber from which the pulverized material is fed into the final storage container. This intermediate storage chamber is alternately aerated and subjected to a pressure which is equal to or greater than the pressure prevailing in the final storage container whereby, during the pressurization portion of the cycle, the pulverized material may be deliver4d from the intermediate chamber into the final storage container.
In order to uniformly evacuate the pulverized material from the final storge container via the rotary feeders, the pressure inside this storage container must be higher than the pneumatic transport pressure at the downstream side of the rotary feeders. It is also vital that the mass inside the final storage container be completely fluid. As a means of fulfilling these two requisite operating conditions, and as disclosed in said copending application Ser. No. 158,612, a pressurized gas must be injected into the final storage container in order to insure the required fluidization and interior pressure. This pressurized gas is typically air and the storage container will be provided with a pressure-regulation device which automatically operates to prevent over pressurization of the storage container.
While apparatus of the type discussed briefly above and disclosed in copending application Ser. No. 158,612 satisfactorily achieve the requisite operating conditions, such apparatus also consumes a considerable quantity of pressurized gas. By way of example, under typical operating conditions a storage enclosure having a diameter of 3.8 m would require 21 kg of pressurized air per minute. These pressurized air requirements can be met only through the use of compressors which are comparatively expensive to install, operate and maintain.